Selective and non-selective barrier layer wet removal

ABSTRACT

A method for manufacturing a semiconductor device includes forming a dielectric layer on a substrate, forming a plurality of openings in the dielectric layer, conformally depositing a barrier layer on the dielectric layer and on sides and a bottom of each one of the plurality of openings, depositing a contact layer on the barrier layer in each one of the plurality of openings, removing a portion of each contact layer from each one of the plurality of openings, and removing a portion of the barrier layer from each one of the plurality of openings, wherein at least the removal of the portion of the barrier layer is performed using an etchant including: (a) a compound selected from group consisting of -azole, -triazole, and combinations thereof; (b) a compound containing one or more peroxy groups; (c) one or more alkaline metal hydroxides; and (d) water.

TECHNICAL FIELD

The field generally relates to semiconductor devices and methods ofmanufacturing same and, in particular, to selective and non-selectiveremoval of a barrier layer during fabrication of a semiconductor devicehaving fully aligned vias (FAVs).

BACKGROUND

Very-Large Scale Integrated (VLSI) circuits and Ultra-Large ScaleIntegrated (VLSI) circuits include interconnect structures havingelectrically conductive wires that connect devices in different levelsof a semiconductor chip to each other. The conductive interconnectsinclude metals, such as, for example, aluminum or copper, insulated bydielectric materials. Trends in the semiconductor industry have led toreduced gate length and chip size, resulting in smaller interconnectstructures. As the interconnect structures decrease in size, overlayerror between elements in the interconnect structure caused bymisalignment during a lithography process, and the resulting reliabilityissues, have become areas of concern to semiconductor manufacturers.

Processing to form metal interconnects or vias that are fully aligned toa first metallization level (M1) and a second metallization level (M2)on the first metallization level has been attempted. The fully alignedmetal interconnects are referred to herein as fully aligned vias (FAVs).In connection with FAV processing, topography from an underlying metalis used to define a via in a non-self-aligned via (non-SAV) direction.Using the topography from an underlying metal to define a via in anon-SAV direction can be very challenging where the underlying level hascertain structures that may be difficult to recess.

SUMMARY

According to an exemplary embodiment of the present invention, a methodfor manufacturing a semiconductor device includes forming a dielectriclayer on a substrate, forming a plurality of openings in the dielectriclayer, conformally depositing a barrier layer on the dielectric layerand on sides and a bottom of each one of the plurality of openings,depositing a contact layer on the barrier layer in each one of theplurality of openings, removing a portion of each contact layer fromeach one of the plurality of openings, and removing a portion of thebarrier layer from each one of the plurality of openings, wherein atleast the removal of the portion of the barrier layer is performed usingan etchant including: (a) a compound selected from group consisting of-azole, -triazole, and combinations thereof; (b) a compound containingone or more peroxy groups; (c) one or more alkaline metal hydroxides;and (d) water.

According to an exemplary embodiment of the present invention, asemiconductor device includes a dielectric layer on a substrate, anopening in the dielectric layer, a first interconnect structurepartially filling the opening in the dielectric layer, wherein the firstinterconnect structure comprises a first barrier layer lining a bottomof the opening and sides of the opening up to a predetermined heightbelow a top of the opening, and a first contact layer on the barrierlayer in each one of the plurality of openings, wherein the firstcontact layer fills the opening to the predetermined height below thetop of the opening. The semiconductor device further includes a secondinterconnect structure on the first interconnect structure, wherein atleast part of the second interconnect structure is in the opening, andincludes a second contact layer on a second barrier layer.

According to an exemplary embodiment of the present invention, a methodfor manufacturing a semiconductor device includes forming a dielectriclayer on a substrate, forming an opening in the dielectric layer,conformally depositing a barrier layer on the dielectric layer and onsides and a bottom of the opening, depositing a contact layer on thebarrier layer in the opening, removing a portion of the contact layerfrom the opening, and removing a portion of the barrier layer from theopening, wherein at least the removal of the portion of the barrierlayer is performed using an etchant including: (a) a compound selectedfrom group consisting of -azole, -triazole, and combinations thereof;(b) a compound containing one or more peroxy groups; (c) one or morealkaline metal hydroxides; and (d) water.

According to an exemplary embodiment of the present invention, anetching composition includes (a) a compound selected from groupconsisting of -azole, -triazole, and combinations thereof; (b) acompound containing one or more peroxy groups; (c) one or more alkalinemetal hydroxides; and (d) water. The etching composition may furtherinclude one or more bidentate or tridentate copper complexants such as,for example, an aminocarboxylic acid, an aminophosphonic acid, adicarboxylic acid, a tricarboxylic acid, a diphosphonic acid, atriphosphonic acid, a carboxyphosphonic acid, or a combination thereof.The etching composition may further include a peroxide stabilizer.

These and other exemplary embodiments of the invention will be describedin or become apparent from the following detailed description ofexemplary embodiments, which is to be read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described belowin more detail, with reference to the accompanying drawings, of which:

FIGS. 1A-1D are cross-sectional views illustrating a method ofmanufacturing a semiconductor device including fully aligned vias (FAVs)according to an exemplary embodiment of the present invention.

FIGS. 2A-2G are three-dimensional views illustrating a method ofmanufacturing a semiconductor device including FAVs according to anexemplary embodiment of the present invention.

FIGS. 3A-3C are graphs illustrating etch rates for tantalum nitride,copper and cobalt, respectively, using an etch chemistry according to anexemplary embodiment of the present invention.

FIGS. 4A-4B are cross-sectional views illustrating a method ofmanufacturing a semiconductor device including FAVs according to anexemplary embodiment of the present invention.

FIGS. 5A-5C are graphs illustrating etch rates for tantalum nitride,copper and cobalt, respectively, using an etch chemistry according to anexemplary embodiment of the present invention.

FIGS. 6A-6E are cross-sectional views illustrating a method ofmanufacturing a semiconductor device including FAVs according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will now be discussed in furtherdetail with regard to semiconductor devices and methods of manufacturingsame and, in particular, to removal of a barrier layer duringfabrication of a semiconductor device having FAVs.

It is to be understood that the various layers and/or regions shown inthe accompanying drawings are not drawn to scale, and that one or morelayers and/or regions of a type commonly used in complementarymetal-oxide semiconductor (CMOS), fin field-effect transistor (FinFET),metal-oxide-semiconductor field-effect transistor (MOSFET), and/or othersemiconductor devices in which aligned contacts may be used, may not beexplicitly shown in a given drawing. This does not imply that the layersand/or regions not explicitly shown are omitted from the actual devices.In addition, certain elements may be left out of particular views forthe sake of clarity and/or simplicity when explanations are notnecessarily focused on the omitted elements. Moreover, the same orsimilar reference numbers used throughout the drawings are used todenote the same or similar features, elements, or structures, and thus,a detailed explanation of the same or similar features, elements, orstructures will not be repeated for each of the drawings.

The semiconductor devices and methods for forming same in accordancewith embodiments of the present invention can be employed inapplications, hardware, and/or electronic systems. Suitable hardware andsystems for implementing embodiments of the invention may include, butare not limited to, personal computers, communication networks,electronic commerce systems, portable communications devices (e.g., celland smart phones), solid-state media storage devices, functionalcircuitry, etc. Systems and hardware incorporating the semiconductordevices are contemplated embodiments of the invention. Given theteachings of embodiments of the invention provided herein, one ofordinary skill in the art will be able to contemplate otherimplementations and applications of embodiments of the invention.

The embodiments of the present invention can be used in connection withsemiconductor devices that may require, for example, CMOSs, MOSFETs,and/or FinFETs. By way of non-limiting example, the semiconductordevices can include, but are not limited to CMOS, MOSFET, and FinFETdevices, and/or semiconductor devices that use CMOS, MOSFET, and/orFinFET technology.

As used herein, “height” refers to a vertical size of an element (e.g.,a layer, trench, hole, etc.) in the cross-sectional andthree-dimensional views measured from a bottom surface to a top surfaceof the element, and/or measured with respect to a surface on which theelement is directly on. Conversely, a “depth” refers to a vertical sizeof an element (e.g., a layer, trench, hole, etc.) in the cross-sectionaland three-dimensional views measured from a top surface to a bottomsurface of the element.

As used herein, “lateral,” “lateral side,” “lateral surface” refers to aside surface of an element (e.g., a layer, opening, etc.), such as aleft or right side surface in the cross-sectional views.

As used herein, “width” or “length” refers to a size of an element(e.g., a layer, trench, hole, etc.) in the figures measured from a sidesurface to an opposite surface of the element.

As used herein, terms such as “upper”, “lower”, “right”, “left”,“vertical”, “horizontal”, “top”, “bottom”, and derivatives thereof shallrelate to the disclosed structures and methods, as oriented in thedrawing figures. For example, as used herein, “vertical” refers to adirection perpendicular to a substrate in the cross-sectional andthree-dimensional views, and “horizontal” refers to a direction parallelto a substrate in the cross-sectional and three-dimensional views.

As used herein, unless otherwise specified, terms such as “on”,“overlying”, “atop”, “on top”, “positioned on” or “positioned atop” meanthat a first element is present on a second element, wherein interveningelements may be present between the first element and the secondelement. As used herein, unless otherwise specified, the term “directly”used in connection with the terms “on”, “overlying”, “atop”, “on top”,“positioned on” or “positioned atop” or the term “direct contact” meanthat a first element and a second element are connected without anyintervening elements, such as, for example, intermediary conducting,insulating or semiconductor layers, present between the first elementand the second element.

Embodiments of the present invention provide a specific method forachieving a fully aligned via landing on a metal interconnect structureincluding a metal contact and a barrier layer around the metal contact.For example, in accordance with an embodiment of the present invention,the metal contact includes, but is not necessarily limited to, copper(Cu) and the barrier layer includes, but is not necessarily limited to,tantalum nitride (TaN). In connection with defining a via in a non-SAVdirection by using the topography from an underlying metal interconnectstructure including, for example, a Cu metal contact and a TaN/Tabarrier layer, the Cu can be selectively removed to form a recess using,for example, standard clean-1/dilute hydrofluoric acid (SC1/dHF), butthere is no known wet or dry process available for selective removal ofa TaN barrier layer. As is known, SC1, can be performed using deionizedwater, aqueous NH₄OH (ammonium hydroxide) and aqueous H₂O₂ (hydrogenperoxide). SC1 can be used in the range of 100:1:1 to 5:1:1 (deionizedwater:hydrogen peroxide:ammonium hydroxide). As is known, dHF is dilutehydroflouric acid and it can be used in the range of 100:1 to 10000:1(DIW:HF (49 wt %).

An exemplary embodiment of the present invention provides for theselective removal of a barrier layer, such as, for example, TaN, withrespect to Cu, cobalt (Co), ruthenium (Ru) and ultra-low K dielectrics(ULKs). An exemplary embodiment of the present invention provides forthe non-selective removal of a barrier layer, such as, for example, TaN,with respect to Cu, and the selective removal of the TaN barrier layerand Cu with respect to Co, Ru and ULKs. In accordance with exemplaryembodiments of the present invention, alkali metal hydroxides when mixedwith hydrogen peroxide are used to perform the selective etching of TaN,and alkali metal hydroxides in combination with hydrogen peroxide, NH₄OHor any Cu complexing agents, are used to etch both TaN and Cu selectiveto Co, Ru and ULKs. Selectivity can be tuned by varying concentrationsof the components. In accordance with an exemplary embodiment of thepresent invention, the addition of triazole to the above chemistries andbuffer pH at ˜9 increases selectivity to cobalt.

FIGS. 1A-1D are cross-sectional views and FIGS. 2A-2G arethree-dimensional views illustrating a method of manufacturing asemiconductor device including fully aligned vias (FAVs) according to anexemplary embodiment of the present invention. Referring to FIGS. 1A and2A, a semiconductor substrate 102 or 202 may comprise semiconductormaterial including, but not limited to, Si, silicon germanium (SiGe),silicon carbide (SiC), silicon germanium carbide (SiGeC), III-V, II-Vcompound semiconductor or other like semiconductor. In addition,multiple layers of the semiconductor materials can be used as thesemiconductor material of the substrate.

In accordance with an embodiment of the present invention, as can beseen in FIGS. 1A and 2A a dielectric layer 105 or 205, which can be, forexample, an interlayer dielectric layer (“ILD”) is deposited on thesubstrate 102 using, for example, deposition techniques including, butnot necessarily limited to, chemical vapor deposition (CVD), plasmaenhanced CVD (PECVD), radio-frequency CVD (RFCVD), physical vapordeposition (PVD), atomic layer deposition (ALD), molecular beamdeposition (MBD), pulsed laser deposition (PLD), and/or liquid sourcemisted chemical deposition (LSMCD), spin-on coating, sputtering, and/orplating. The dielectric layer 105 or 205 may include, but is not limitedto, ULK materials, such as, for example, porous silicates, carbon dopedoxides, silicon dioxides, silicon nitrides, silicon oxynitrides,carbon-doped silicon oxide (SiCOH) and porous variants thereof,silsesquioxanes, siloxanes, or other dielectric materials having, forexample, a dielectric constant in the range of about 2 to about 4. Thedielectric layer 105 or 205 may have a vertical thickness ranging fromabout 20 nm to about 200 nm.

Interconnect structures including a barrier layer 110 or 210 and anelectrically conductive contact 120 on the barrier layer 110, or anelectrically conductive contact 220 on the barrier layer 210 are formedin openings in the dielectric layer 105 or 205, using, for example, asingle or dual damascene technique. In accordance with an embodiment ofthe present invention, the barrier layers 110, 210 are conformallydeposited on portions of the dielectric layers 105, 205 using depositiontechniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD,MBD, PLD, and/or LSMCD, sputtering, and/or plating, and then theelectrically conductive contacts 120, 220 are respectively deposited onthe barrier layers 110, 210 using, for example, one or more of theabove-noted deposition techniques. According to an embodiment of thepresent invention, the barrier layers 110, 210 comprise TaN. Othermaterials for the barrier layers 110, 210 can include, but are notnecessarily limited to, Ta, titanium (Ti), titanium nitride (TiN) and abilayer of TaN/Ta, which, like TaN, can be selectively andnon-selectively removed in accordance with embodiments of the presentinvention described herein. According to an embodiment of the presentinvention, the contacts 120, 220 comprise copper, cobalt and/orruthenium.

Liner layers (not shown), such as, for example, cobalt or ruthenium canbe positioned between the barrier and contact layers. For example,cobalt can be present in thin layers as a liner layer (e.g., 1 to 100angstroms) between a TaN barrier layer, and a Cu contact layer. Whencobalt or another liner layer is present, the liner layer can be removedduring the contact removal step in, for example, the SC1/dHF process.

After deposition of the contacts 120, 220, a planarization process, suchas, chemical mechanical planarization (CMP), is performed to planarizean upper surface of the dielectric layer 105. Referring to FIG. 1A, inaccordance with an embodiment of the present invention, theplanarization can be down to the barrier layer 110 so that a planarizedbarrier layer 110 remains on a top surface of the dielectric layer 105,as well as on side and bottom surfaces of the openings in the dielectriclayer 105 where the contacts 120 are formed. A thickness of the barrierlayer 110 on a top surface of the dielectric layer 105, as well as onside and bottom surfaces of the openings in the dielectric layer 105 canbe in the range of about 0.5 nm to about 10 nm. Alternatively, referringto FIG. 2A, the planarization can be down to the dielectric layer 205 sothat the barrier layer 210 remains on side and bottom surfaces of theopenings in the dielectric layer 205 where the contacts 220 are formed,and not on a top surface of the dielectric layer 205. A thickness of thebarrier layer 210 on side and bottom surfaces of the openings in thedielectric layer 205 can be in the range of about 0.5 nm to about 10 nm.

Referring to FIG. 1B, the contact portions 120 (e.g., copper) arerecessed in the openings in the dielectric layer 105 using, for example,SC1/dHF. As an alternative to using SC1/dHF, the contact portions 120may recessed by an etching technique, such as, for example, wet etches,including chemistries having an oxidizer, such as, for example, hydrogenperoxide, Cu complexing agent, such as, for example amino acids,carboxylic acids.

As can be seen in FIG. 1B, according to an embodiment of the presentinvention, the contacts 120 are recessed selective to the barrier layer110 so that the barrier layer 110 remains adjacent areas where thecontacts 120 were removed. The contacts 120 are also recessed selectiveto the dielectric layer 105 and may be recessed to depths (d₁, d₂),respectively from a top surface of the dielectric layer 105. The firstrecessed depth (d₁) may be the same as the second depth (d₂), and mayrange from about 5 nm to 50 nm. The contact 120 of each opening may berecessed at the same time.

Referring to FIG. 1C, after recessing of the contacts 120 (e.g., coppercontacts), the barrier layer 110 (e.g., TaN) is removed from the topsurface of the dielectric layer 105 and from the portions of theopenings down to depths d₁ and d₂. The removal of the barrier layer 110is selective to the contact layers 120 (e.g., Cu) and the dielectriclayer 105 (e.g., ULK material). According to an embodiment of thepresent invention, the barrier layer 110 is selectively etched using,for example, 15% H₂O₂ (hydrogen peroxide)+10 g/L (grams/liter) BTA(Benzotriazole)+0.5 g/L CDTA (cyclohexanediamininetetraaceticacid)+KOH(potassium hydroxide) in deionized (DI) water at a pH in the range ofabout 4 to about 12. Etching can be performed at a temperatures rangingfrom about 25° C. to about 70° C. Other possible variations for etchchemistry include, but are not necessarily limited to:

(a) Replacing KOH by another alkaline metal hydroxide, such as, forexample, one of LiOH, NaOH, RbOH, CsOH, and combinations thereof, atconcentration ranges of about 0.001 M to about 0.1 M (molar);

(b) Replacing hydrogen peroxide by another compound containing one ormore peroxy groups, such as, for example, one of perborate salts,percarbonate, urea-hydrogen peroxide, and combinations thereof, atconcentration ranges of about 1% to about 20%;

(c) Replacing CDTA by another peroxide stabilizer, such as, for example,one of diethylenetriaminepenta(methylene-phosphonic acid) (DTPMPA), andethylenediaminetetraacetic acid (EDTA) at concentration ranges of about0.1 g/L to about 1 g/L; and

(d) Replacing BTA by another corrosion inhibitor, such as, for example,one of 1,2,3 triazole, 1,3,4 triazole, 1,2,4 triazole, imidazole,methyl-thiol-triazole, thiol-triazole, triazole acid,5-methyl-1H-benzotriazole, at concentration ranges of about 0.1 g/L toabout 10 g/L.

In addition to selectively etching TaN with respect to copper and ULKmaterials, the etch chemistry described in connection with FIG. 1C, alsoselectively etches TaN with respect to cobalt and ruthenium, so that abarrier layer comprising TaN can be selectively removed with respect toa structure comprising copper, cobalt and/or ruthenium to result in thestructure illustrated in FIG. 1C.

FIGS. 3A-3C are graphs illustrating etch rates for tantalum nitride,copper and cobalt, respectively, using the etch chemistry described inconnection with FIG. 1C, according to an exemplary embodiment of thepresent invention. Referring to graph 310 in FIG. 3A, the etch rate ofTaN at 60° C. using 15% H₂O₂+10 g/L BTA+0.5 g/L CDTA+KOH at a pH of 9 isapproximately 48 angstroms/minute. Referring to graph 320 in FIG. 3B,the etch rate of copper under the same conditions as in FIG. 3A isapproximately 6 angstroms/minute. Referring to graph 330 in FIG. 3C, theetch rate of cobalt under the same conditions as in FIG. 3A isapproximately <1 angstrom/minute. Accordingly, when using the etchchemistry described in connection with FIG. 1C, the TaN:Cu wet etchselectivity is approximately 8:1, and the TaN:Co wet etch selectivity isapproximately 48:1 or higher. Therefore, the TaN can be selectivelyetched with respect to Cu and Co. In addition, although not shown in thegraphs, the ULK etch rate is <1 Å/min, so TaN:ULK is 48:1 or higher.

FIG. 2B illustrates a three-dimensional view of what is shown in FIG.1C, and may be the result of selective removal of the barrier layer 210after selective removal of top portions of the contact layers 220 usingthe same or similar processing steps described in connection FIGS. 1Band 1C. Alternatively, the structure in FIG. 2B can also represent theresult of processing similar to that described below in connection withFIGS. 4A and 4B, where both the barrier and contact layers aresimultaneously or substantially simultaneously removed selective to ULKmaterials, cobalt and/or ruthenium.

Processing to result in the structures illustrated in FIGS. 1D and 2Gwill now be described in connection with FIGS. 2C-2F. Referring to FIG.2C, a cap layer 230 is formed on the structure of FIG. 2B. Similarly, acap layer 130 is formed on the structure of FIG. 1C. As can be seen inFIG. 2C, the cap layer 230 may be deposited using a suitable depositiontechnique, such as, for example, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD,and/or LSMCD, sputtering, and/or plating, on the dielectric layer 205and on the remaining interconnect structures comprising the barrierlayer 210 and the metal contacts 220. The cap layer 230 can include adielectric material, such as, for example, silicon nitride (SiN),silicon carbide (SiC), silicon carbonitride (SiCN), hydrogenated siliconcarbide (SiCH), or other suitable material. The cap 230 can have avertical thickness ranging from about 1 nm to about 30 nm. The cap 230may function as an air and/or metal diffusion barrier or insulator, andmay be used to improve interconnect reliability.

Referring to FIG. 2D, another dielectric layer 205′ is formed on the caplayer 230. Dielectric layer 205′ may comprise the same or similarmaterials as those of dielectric layers 105 and 205, and can also bereferred to as an ILD layer. Dielectric layer 105′ in FIG. 1Dcorresponds to dielectric layer 205′. Dielectric layer 205′ may beformed using the same or similar deposition techniques as those used forforming dielectric layers 105 and 205, and may be planarized using, forexample, CMP.

Referring to FIG. 2D, hardmasks 270 and 280 are sequentially formed onthe dielectric layer 205′. The hardmask 270 may be a suitable maskingmaterial sacrificial in nature, such as, for example, a low-k siliconcarbide (SiC), silicon carbonitride (SiCN) or silicon nitride (SiN). Thehardmask 280 is formed on the hardmask 270, and may be a suitablemasking material, such as, for example, titanium nitride (TiN).According to an embodiment, the hardmask 280 is a different materialfrom the hardmask 270 to permit etching of the hardmask 280 selective tothe hardmask 270, such that hardmask 280 is etched and the hardmask 270functions as an etch stop. The hardmasks 270, 280 can be formed using adeposition technique, such as, for example, CVD, PECVD, RFCVD, PVD, ALD,MBD, PLD, and/or LSMCD, sputtering, and/or plating. According to anembodiment of the present invention, the hardmask 270 is deposited by aCVD process that does minimal or no damage to an underlying dielectriclayer 205′, and protects the dielectric layer 205′ from plasma of a PVDdeposition of the hardmask 280.

As shown in FIG. 2D, the hardmask 280 is etched into a trench pattern,using, for example, a reactive ion etch (RIE) process. As noted above,the hardmask 270 can function as an etch stop for the formation of thetrench pattern, as portions of the hardmask 280 are removed selective tothe hardmask 270 to pattern the hardmask into the trench pattern. Asillustrated, the trench pattern formed from hardmask 280 extendsperpendicular to, and overlaps at least a portion of the contacts 220.

Referring to FIG. 2E, a resist 290 is formed on the remaining portionsof hardmask 280 and on portions of hardmask 270. The resist 290 caninclude masking materials that are used in lithography, such as, forexample, organic resist coatings or patterning layers. The resist can beformed using, for example, spin coating and may include one or morelayers. The resist 290 can have a thickness ranging from about 5 nm to500 nm. A via pattern 292 is formed using the resist 290, along withlithography and patterning techniques.

As can be seen, the via pattern 292 is aligned with the leftinterconnect structure comprising the barrier and contact layers 210 and220. Another via pattern can be formed to align with a portion of theright interconnect structure. Via patterns can be self-aligned by thehardmask 280 because of overlapping the hardmask 280 and a selectiveetching technique, where the resist 290 is etched selectively withrespect to hardmask 280 using an etching technique, such as, forexample, RIE.

In a non-limiting illustrative embodiment, as shown in FIG. 2E, a viapattern, such as via pattern 292, is formed through the hardmask 270 andpartially through the dielectric layer 205′. Alternatively, a viapattern is formed through both the hardmask 270 and the dielectric layer205′, or formed partially through the hardmask 270 without reaching thedielectric layer 205′. A depth of a via pattern can be a function ofetch selectivity of the materials used or a desired via depth.

Referring to FIG. 2F, the resist 290 is removed and trenches 297 a and297 b are etched. The resist 290 is removed using, for example, RIE orstripping processes. The trenches 297 a, 297 b are formed based on thepattern of the hardmask 280, and can be etched using, for example, anRIE, or other etching process. The etching of the trenches 297 a, 297 bmay be selective to the hardmask 280.

Referring to FIG. 2G, a next level of interconnect structures includingbarrier layers 210′ and contact layers 220′ is deposited in the firstand second trenches 297 a, 297 b, respectively. Similarly, referring toFIG. 1D, a next level interconnect structure includes a barrier layer110′ and contact layer 120′ deposited in a trench over the lower levelinterconnect structure including barrier and contact layers 110, 120.The barrier and contact layers 110′, 210′, 120′, 220′ can includedifferent, the same or substantially the same materials as the barrierand contact layers 110, 210 and 120, 220. Accordingly, like the contactlayers 120, 220, the contact layers 220′ may include conductivematerials, such as, for example, copper, cobalt and/or ruthenium, andthe barrier layers 110′, 210′, like the barrier layers 110, 210, cancomprise TaN, Ta, TaN/Ta, Ti and TiN. According to an embodiment of thepresent invention, the barrier layers 110, 110′, 210, 210′ each includeTaN, and the contact layers 120, 120′, 220, 220′ comprise copper.

The next level interconnect structures are fabricated using the same orsimilar techniques to the lower level interconnect structures. Forexample, depending on the configuration of the trenches for receivingthe next level interconnect structures, the barrier layers 110′, 210′are conformally deposited on portions of the lower and upper leveldielectric layers 105, 105′ or 205, 205′, and on portions of the lowerlevel interconnect structures using deposition techniques including, butnot limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD,sputtering, and/or plating. The electrically conductive contacts 120′,220′ are respectively deposited on the barrier layers 110′, 210′ using,for example, one or more of the above-noted deposition techniques.Referring to FIGS. 1D and 2G, according to an embodiment of the presentinvention, the structure can be planarized down to the upper dielectriclayer 105′, 205′, thereby removing hardmasks 270, 280.

According to an embodiment, referring to FIGS. 1D and 2G, a bottomportion of a next level interconnect structure is on an upper surface ofa lower level interconnect structure, wherein an interface between thenext level interconnect structure and the lower level interconnectstructure is in an opening of the dielectric layer 105, 205 at apredetermined height below a top of the opening. The predeterminedheight can be, for example, at or near the depth to which the lowerlevel interconnect structure was recessed.

FIGS. 4A-4B are cross-sectional views illustrating a method ofmanufacturing a semiconductor device including FAVs according to anexemplary embodiment of the present invention. FIG. 4A illustrates astructure and processing which are the same or similar to the structureand processing shown in FIG. 1A. In accordance with an embodiment of thepresent invention, as can be seen in FIG. 4A, a dielectric layer 405,like dielectric layer 105, is deposited on the substrate 402 using, forexample, deposition techniques including, but not necessarily limitedto, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, LSMCD, sputtering, and/orplating.

Interconnect structures including a barrier layer 410 and anelectrically conductive contact 420 on the barrier layer 410, the sameor similar to barrier and contact layers 110, 120, are formed inopenings in the dielectric layer 405, using, for example, the same orsimilar techniques as those described in connection with barrier andcontact layers 110, 120. After deposition of the contacts 420, aplanarization process, such as CMP, is performed down to the barrierlayer 410 so that like the structure in FIG. 1A, a planarized barrierlayer 410 remains on a top surface of the dielectric layer 405, as wellas on side and bottom surfaces of the openings in the dielectric layer405 where the contacts 420 are formed.

In accordance with the embodiment illustrated in FIG. 4B, the contactlayer 420 comprises copper and the barrier layer 410 comprises TaN.Referring to FIG. 4B, after planarization described in connection withFIG. 4A, both the TaN barrier layer 410 and Cu contact layer 420 areselectively recessed in a single etching process using, for example, 15%H₂O₂+10 g/L BTA+0.1 M (moles) NH₃ (ammonia)+0.5 g/L CDTA+KOH in DI waterat a pH range of about 4 to about 12. Etching can be performed at atemperature range of about 25° C. to about 70° C. As noted above, otherpossible variations for etch chemistry include, but are not necessarilylimited to:

(a) Replacing KOH by another alkaline metal hydroxide, such as, forexample, one of LiOH, NaOH, RbOH, CsOH, and combinations thereof, atconcentration ranges of about 0.001 M to about 0.1 M (molar);

(b) Replacing hydrogen peroxide by another compound containing one ormore peroxy groups, such as, for example, one of perborate salts,percarbonate, urea-hydrogen peroxide, and combinations thereof, atconcentration ranges of about 1% to about 20%;

(c) Replacing CDTA by another peroxide stabilizer, such as, for example,one of diethylenetriaminepenta(methylene-phosphonic acid) (DTPMPA), andethylenediaminetetraacetic acid (EDTA) at concentration ranges of about0.1 g/L to about 1 g/L; and

(d) Replacing BTA by another corrosion inhibitor, such as, for example,one of 1,2,3 triazole, 1,3,4 triazole, 1,2,4 triazole, imidazole,methyl-thiol-triazole, thiol-triazole, triazole acid,5-methyl-1H-benzotriazole, at concentration ranges of about 0.1 g/L toabout 10 g/L.

NH₃ (ammonia) in water can be from one of the sources NH₄OH (ammoniumhydroxide), ammonium phosphate, or ammonium dihydrogen phosphate. Othercomplexing agents such as, bidentate or tridentate copper complexantsincluding amino carboxylic acids (amino acids), amino phosphonic acids,di and tri-carboxylic acids, di and tri-phosphonic acids,carboxyphosphonic acids, or combinations thereof, can be used in placeof NH₃ (ammonia).

This etch chemistry selectively etches both TaN and Cu with respect toULK materials, and also selectively etches TaN and Cu with respect tocobalt and ruthenium, so that a barrier layer comprising TaN and acontact layer comprising copper can both be selectively removed in thesame etch step with respect to ULK materials and/or cobalt andruthenium, to result in the structure illustrated in FIG. 4B. Accordingto an embodiment of the present invention, the ammonia is added viaNH₄OH (ammonium hydroxide), and etch selectivity of TaN with respect toCu can be altered by modifying amounts of ammonia. Referring to FIG. 4B,the barrier and contact layers 410 and 420 are removed from a topsurface of the dielectric layer 405 and from portions of openings in thedielectric layer 405 down to depths d₃ and d₄ measured from a topsurface of the dielectric layer 405. The recessed depth (d₃) may be thesame as the depth (d₄), and may range from about 5 nm to 50 nm.

FIGS. 5A-5C are graphs illustrating etch rates for tantalum nitride,copper and cobalt, respectively, using the etch chemistry described inconnection with FIG. 4B, according to an exemplary embodiment of thepresent invention. Referring to graph 510 in FIG. 5A, the etch rate ofTaN at 60° C. using 15% H₂O₂+10 g/L BTA+0.1 M NH₃+0.5 g/L CDTA+KOH at apH range of about 4 to about 12, is approximately 40 angstroms/minute.Referring to graph 520 in FIG. 5B, the etch rate of copper under thesame conditions as in FIG. 5B is approximately 33 angstroms/minute.Referring to graph 530 in FIG. 5C, the etch rate of cobalt under thesame conditions as in FIG. 5A is approximately <1 angstrom/minute.Accordingly, when using the etch chemistry described in connection withFIG. 4B, the TaN:Cu wet etch selectivity is approximately 1:1, and theTaN:Co wet etch selectivity is approximately 40:1 or higher. Therefore,both Cu and TaN can be selectively etched with respect to Co. Inaddition, although not shown in the graphs, the ULK etch rate is <1Å/min, so TaN:ULK is 40:1 or higher.

Further processing similar to that described in connection with FIG. 1Dand FIGS. 2C-2G can be performed on the structure of FIG. 4B to resultin semiconductor devices the same or similar to those depicted in FIGS.1D and 2G. For the sake of brevity, repetitive descriptions of suchprocessing are not repeated.

FIGS. 6A-6E are cross-sectional views illustrating a method ofmanufacturing a semiconductor device including FAVs according to anexemplary embodiment of the present invention. FIGS. 6A-6B illustratestructures and processing which are the same or similar to the structureand processing shown in FIGS. 1A-1B. In accordance with an embodiment ofthe present invention, as can be seen in FIG. 6A, a dielectric layer605, like dielectric layer 105, is deposited on the substrate 602 using,for example, deposition techniques including, but not necessarilylimited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, LSMCD, sputtering,and/or plating.

Interconnect structures including a barrier layer 610 and anelectrically conductive contact 620 on the barrier layer 610, the sameor similar to barrier and contact layers 110, 120, are formed inopenings in the dielectric layer 605, using, for example, the same orsimilar techniques as those described in connection with barrier andcontact layers 110, 120. After deposition of the contacts 620, aplanarization process, such as CMP, is performed down to the barrierlayer 610 so that like the structure in FIG. 1A, a planarized barrierlayer 610 remains on a top surface of the dielectric layer 605, as wellas on side and bottom surfaces of the openings in the dielectric layer605 where the contacts 620 are formed.

Referring to FIG. 6B, like the contact portions 120, the contactportions 620 (e.g., copper) are recessed in the openings in thedielectric layer 605 using, for example, SC1/dHF. As an alternative tousing SC1/dHF, the contact portion 620 may recessed by an etchingtechnique, such as, for example, an RIE technique and/or wet etches asdiscussed above. The contacts 620 are recessed selective to the barrierlayer 610 so that the barrier layer 610 remains adjacent areas where thecontacts 120 were removed. The contacts 620 are also recessed selectiveto the dielectric layer 605 and may be recessed to depths (d₅, d₆),respectively from a top surface of the dielectric layer 605.

Referring to FIG. 6C, after recessing of the contacts 620 (e.g., coppercontacts), instead of proceeding with removal of the barrier layers 610as in FIG. 1C, cap layers 650 are deposited on the recessed portions ofthe contact layers 620. The cap layers comprise, for example, a metal,such as, but not necessarily limited to, cobalt, ruthenium, manganese(Mn), manganese oxide (MnO), manganese nitride (MnN), and cobalttungsten phosphide (CoWP). The cap layers 650 can have a verticalthickness in the range of about 0.5 nm to about 8 nm. The cap layers 650are deposited to prevent unwanted loss of portions of the contact layers620 (e.g., copper contact layers) during subsequent removal of thebarrier layers 610. The cap layers 650 can be deposited using, forexample, techniques, including, but not necessarily limited to, CVD,PECVD, RFCVD, PVD, ALD, MBD, PLD, LSMCD, sputtering, and/or plating.

Referring to FIG. 6D, after deposition of the cap layers 650, similar tothe processing described in connection with FIG. 1C, the barrier layer610 (e.g., TaN) is removed from the top surface of the dielectric layer605 and from the portions of the openings down to depths d₅ and d₆. Theremoval of the barrier layer 610 is selective to the contact layers 620(e.g., Cu), the dielectric layer 605 (e.g., ULK material), and to thecap layers 650. For example, as noted in connection with FIG. 3C, theTaN:Co wet etch selectivity is approximately 48:1 or higher when usingthe etchant described in connection with FIG. 1C. As noted above, thecap layers 650 protect the contact layers 620 from inadvertent removal.According to an embodiment of the present invention, the barrier layer610 is selectively etched using, for example, the same etchant asdescribed in connection with FIG. 1C.

Further processing similar to that described in connection with FIG. 1Dand FIGS. 2C-2G can be performed on the structure of FIG. 6D to resultin the structure in FIG. 6E, which is similar to the semiconductordevices depicted in FIGS. 1D and 2G, except for the inclusion of the caplayers 650 on the recessed contact portions 620. For the sake ofbrevity, repetitive descriptions of such processing are not repeated,noting that like numerals (e.g., 605′, 610′, 620′ and 630) refer to likeelements in the specification.

Although illustrative embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various other changes and modifications may bemade by one skilled in the art without departing from the scope orspirit of the invention.

We claim:
 1. A semiconductor device, comprising: a dielectric layer on asubstrate; an opening in the dielectric layer; a first interconnectstructure partially filling the opening in the dielectric layer, whereinthe first interconnect structure comprises: a first barrier layer lininga bottom of the opening and sides of the opening up to a predeterminedheight below a top of the opening; and a first contact layer on thefirst barrier layer in the opening, wherein the first contact layerfills the opening to the predetermined height below the top of theopening; a second interconnect structure on the first interconnectstructure, wherein at least part of the second interconnect structure isin the opening, and includes a second contact layer on a second barrierlayer; an additional opening in the dielectric layer; and a thirdinterconnect structure partially filling the additional opening in thedielectric layer.
 2. The semiconductor device according to claim 1,further comprising a metal cap layer between the first and secondinterconnect structures.
 3. The semiconductor device according to claim2, wherein the metal cap layer is selected from the group consisting ofcobalt, ruthenium and manganese.
 4. The semiconductor device accordingto claim 2, wherein the second barrier layer is formed on the metal caplayer.
 5. The semiconductor device according to claim 1, wherein thefirst and second barrier layers comprise tantalum nitride and the firstand second contact layers comprise copper.
 6. The semiconductor deviceaccording to claim 1, further comprising a dielectric cap layer on thethird interconnect structure, wherein at least part of the dielectriccap layer is in the additional opening.
 7. The semiconductor deviceaccording to claim 6, wherein the dielectric cap layer lines sides of aportion of the additional opening.
 8. The semiconductor device accordingto claim 6, further comprising a metal cap layer on the thirdinterconnect structure between the dielectric cap layer and the thirdinterconnect structure.
 9. The semiconductor device according to claim6, further comprising an additional dielectric layer on the dielectriccap layer.
 10. The semiconductor device according to claim 6, wherein aportion of the second barrier layer is formed on a portion of thedielectric cap layer.
 11. The semiconductor device according to claim10, wherein the portion of the second barrier layer that is formed onthe portion of the dielectric cap layer is on a top surface of thedielectric layer.
 12. A semiconductor device, comprising: a dielectriclayer on a substrate; a plurality of openings in the dielectric layer; afirst interconnect structure partially filling the plurality of openingsin the dielectric layer, wherein the first interconnect structurecomprises: a first barrier layer lining a bottom and sides of each ofthe plurality of openings up to a predetermined height below a top ofeach of the plurality of openings; a first contact layer on the firstbarrier layer in of each of the plurality of openings, wherein the firstcontact layer fills each of the plurality of openings to thepredetermined height below the top of each of the plurality of openings;and a second interconnect structure on the first interconnect structurein a first opening of the plurality of openings, wherein at least partof the second interconnect structure is in the first opening of theplurality of openings, and includes a second contact layer on a secondbarrier layer.
 13. The semiconductor device according to claim 12,further comprising: a metal cap layer between the first and secondinterconnect structures in the first opening of the plurality ofopenings.
 14. A semiconductor device, comprising: a dielectric layer ona substrate; a plurality of openings in the dielectric layer; a firstinterconnect structure partially filling the plurality of openings inthe dielectric layer, wherein the first interconnect structurecomprises: a first barrier layer lining a bottom and sides of each ofthe plurality of openings up to a predetermined height below a top ofeach of the plurality of openings; and a first contact layer on thefirst barrier layer in of each of the plurality of openings, wherein thefirst contact layer fills each of the plurality of openings to thepredetermined height below the top of each of the plurality of openings;a dielectric cap layer on the first interconnect structure in a secondopening of the plurality of openings, wherein at least part of thedielectric cap layer is in the second opening, and lines sides of aportion of the second opening from a top of the second opening to thefirst barrier layer in the second opening; and a metal cap layer on thefirst interconnect structure in the second opening of the plurality ofopenings between the dielectric cap layer and the first interconnectstructure.
 15. The semiconductor device according to claim 14, furthercomprising an additional dielectric layer on the dielectric cap layer.